1. Field of the Invention
This invention relates to a three piece wheel for use in an automobile.
2. Discussion of the Related Art
FIGS. 1 and 2 show cross-section views of three piece automobile wheels. In the aluminum wheels shown in the figures, an inner rim 11, 21, outer rim 12, 22, and center disc 13, 23 are rigidly joined by fastening bolts 14, 24. Opposing regions of the inner rim 11, 21 and the outer rim 12, 22 bend inwards to establish a flange section 15, 25, and fastening bolts 14, 24 pass through the center disc 13, 23 and this flange section 15, 25 to rigidly join the wheel as a unit.
The three piece wheel of FIG. 1 is a known aluminum wheel provided with a trough 17 in both the inner rim 11 and the outer rim 12. The trough 17 is necessary for installing a tire 120 on the wheel. This is because the bead region 121 of the tire 120 has an inside diameter which is smaller than the outside diameter of the rim flange 16. As a result, the tire 120 cannot be set in place, with the entire perimeter of the bead region 121 in the plane of the rim 18, unless one part of the bead region 121 is placed in the trough 17 allowing it to pass over the rim flange 16. The aluminum wheel shown in FIG. 1 has a trough 17 established in its outer rim 12, and a valve 110 passes through, and is fixed to the side-wall 117 of the trough 17. The valve 110 has a base 111 disposed inside the wheel and a stem 112 is fixed to the valve opening 113. The stem 112 is outside of the center disc 13 and is exposed outside the wheel.
Since the three piece wheel of FIG. 1 is provided with a trough 17 in its outer rim 12 and the outer perimeter of the center disc 13 is attached to the bottom of the trough 17, the outside diameter of the center disc 13 becomes small. A three piece wheel, which has a small center disc 13 outside diameter for a given rim outside diameter, has the drawback that a high quality aesthetic design is not possible. This is because a high quality design can be achieved by increasing the size of the center disc, which is more aesthetically pleasing than the rim, and increasing the diameter of the track of the fastening bolts attached at the outer perimeter of the center disc. Many users of aluminum wheels give priority to wheel design over function. In particular, users, who install aluminum wheels to improve the aesthetic design of an automobile, generally install aluminum wheels with center discs which are as large as possible. For this reason, it is very important to increase the outside diameter of the center disc of a three piece wheel.
The aluminum wheel of FIG. 1 also has the drawback that the valve 110 can damage the tire 120 when driving after the tire 120 has punctured. This is because the punctured and deflated tire 120 bead region 121, which is internally reinforced with bead wire, becomes separated from the rim flange 16, moves inward, and abrades against the valve 110 base 111. In particular, when an automobile is driven after puncture and deflation, the bead region 121 of the tire 120 can strike the valve 110 base 111 with significant force and cause considerable tire 120 damage after drifting only slightly away from the rim flange 16. As a result, a tire 120 with a damaged bead region 121 cannot be driven on again even if the puncture is repaired. From a traffic safety viewpoint, an automobile cannot always stop immediately if a tire puncture occurs. For example, if tire puncture occurs on a high speed roadway such as a freeway, it is necessary to move the vehicle to a safe pull-off area. If the tire 120 bead region 121 is damaged while driving to a pull-off area, the tire cannot be driven on again even if the puncture is repaired. Tire repair on a high speed roadway can be performed by repair personnel who can come to the site. In this case, repair personnel cannot bring an assortment of tire types, that fit all types of automobiles, to the repair site. This is because the number of different types of tires is extremely large. As a result, it is very important to be able to drive on a tire after the puncture is repaired at the site. An automobile, which cannot be driven even after puncture repair, must be moved by being towed by a wrecker. Compared to puncture repair, towing an automobile with a punctured tire using a wrecker is much more troublesome and service costs are much higher. This is because wrecker fees are incurred in addition to the cost of tire replacement. Further, towing an automobile with a wrecker on a high speed roadway is definitely not desirable from a traffic safety viewpoint. An automobile can also be moved by placement on a cargo truck, but this method can incur even more cost. Therefore, reducing tire damage caused by driving on a punctured tire is extremely important from both a safety standpoint and an economic standpoint.
In the three piece wheel shown in FIG. 2, a trough 27 is provided in the inner rim 21 but not in the outer rim 22. In a three piece wheel with this structure, the outside diameter of the center disc 23 can be made larger. This is because the center disc 23 can be fixed to the outer rim 22, which has no trough 27. However, if an automobile is driven after puncturing a tire 220 with a three piece wheel having this structure, the tire 220 can still be damaged considerably. In a three piece wheel of this structure, although the valve 210 is disposed with separation from the rim flange 26 where the tire bead region 221 is mounted, the valve 210 still projects beyond the plane of the rim 28. Therefore, the wheel has the drawback that if the bead region 221 of a punctured and deflated tire 220 drifts to the position of the valve 210 the bead region 221 can be damaged considerably. When a punctured and deflated tire 220 is driven on, it is impossible to totally avoid movement of the tire bead region 221 to the center region of the plane of the rim 28. Consequently, bead region damage incurred by driving on a punctured tire 220 cannot be reliably prevented by a configuration which disposes the valve base 211 in the center region separated from the rim flanges 26. In particular, valves 210 housing tire 220 air pressure sensors, which are becoming prevalent recently, have extremely large assemblies that project beyond the plane of the rim 28. As a result, a large projecting assembly can cause substantial damage when a punctured tire 220 is driven on. In addition, since the pressure sensor assembly projects beyond the plane of the rim 28, the pressure sensor can be directly pressed upon by the force of the punctured tire 220 resulting in its failure when the punctured tire 220 is driven on. Further, in in FIG. 2, reference numeral 212 shows a stem of valve 210.
The present invention was developed to correct these types of drawbacks seen in related art three piece wheels. Thus it is a primary object of the present invention to provide a three piece automobile wheel which can reduce damage to the tire bead region when a punctured tire is driven on, while increasing the size of the center disc to allow high quality design. Another important object of the present invention is to provide a three piece automobile wheel which can use a valve type which houses a pressure sensor, and prevent its failure when tire puncture occurs.